CHAPTER 8

1. Web Server
Hardware and
Software
CHAPTER 8
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.

2. Learning Objectives
In this chapter, you will learn:
• How a Web server performs its basic functions
• What operating system and server software is used on Web
servers
• How to identify and manage e-mail and spam control issues
• How commonly used Internet and Web site utility programs
work
• What hardware online businesses use to power their Web
sites
• How cloud computing and content delivery networks are
providing new Web infrastructure
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3. Introduction
• Case study: Israel’s Channel 2 News
– Produces news content and programming for other
Channel 2 shows, Web sites and its mobile device app
• Web site and mobile app offer many high-resolution
photographs and video chips
– Online news organizations face wide variation in user
interest levels and need for Internet bandwidth
• Breaking news events lead to high demands on the Web
site and mobile app and can result in system overload
• Peak periods in news business can be unpredictable
• As a solution, Channel 2 uses Google Cloud Computing
to store content
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4. Web Server Basics
• Client/server architectures used in LANs, WANs, Web
– Server computers have more memory and larger, faster
disk drives than the client computers they serve
• Web browser: a type of Web client software
• Platform neutrality is the ability of a network to connect
devices using different operating systems
– Critical in rapid spread, widespread Web acceptance
• Web server’s main job to respond to Web client
requests
– Main elements: Hardware, operating system software,
and Web server software
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FIGURE 8-1 Platform neutrality of the Web
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6. Dynamic Content Generation
• Static page is an unchanging page retrieved from
stored Web server file(s)
• Dynamic page created in response to user request
– Customized pages give user an interactive experience
• Client-side scripting software operates on the Web client
(browser) and changes Web page display in response to
a user’s actions (JavaScript or Adobe Flash)
• Server-side scripting program runs on a Web server and
creates Web page in response to request for specific
information from a Web client
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7. Dynamic Content Generation (cont’d.)
• Software tools to create dynamic Web pages
– Microsoft ASP.NET, Apache Software Foundation
Hypertext Preprocessor (PHP) and Adobe ColdFusion
– AJAX (asynchronous JavaScript and XML) creates
interactive Web sites that look like applications
• Ruby on Rails, Scala and Python (scripting language)
are used to accomplish the same objectives
• Many Web sites use more than one language and/or
development framework to accomplish specific
objectives
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8. Multiple Meanings of “Server”
• Server is any computer providing files or making
programs available to other computers connected to
it through a network
– Server software makes files and programs available
• May be part of the operating system (OS) and be
referred to as server software (confusing)
• Some servers connected to Internet via a router
– Runs Web server software that makes server’s files
available to other computers and called a Web server
• E-mail server: handles incoming and outgoing e-mail
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9. Multiple Meanings of “Server” (cont’d.)
• Database server runs database management
software
• Transaction server runs accounting and inventory
management software
• “Server” describes several types of computer
hardware and software
– Context needed to determine the intended meaning
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10. Web Client/Server Architectures
• Web browser requests files from Web server and
uses the Internet as the transportation medium
– Request formatted by browser using HTTP and sent
to server computer
– Server receives request, retrieves requested Web
page file, formats using HTTP, and sends back to
client over the Internet
– Client Web browser software displays page
• Repeating process of request, response, display
• Web page with graphics can be slow because each
page element requires separate request and response
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11. Web Client/Server Architectures (cont’d.)
• Basic model is two-tier client/server architecture
– One client and one server computer
• Request message is the Web client message sent to
request file(s) from a Web server that consists of
three major parts
– Request line contains command, target resource
name, protocol name, version number
– Optional request headers contain file type information
client accepts
– Optional entity body is used to pass bulk information
to server
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FIGURE 8-2 Message flows in a two-tier client/server network
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13. Web Client/Server Architectures (cont’d.)
• Server receiving request message executes
command included in message
– Retrieves Web page file from disk and creates a
response message to send back to client
– Identical in structure to request message (slightly
different function)
• Response header line indicates server HTTP version,
response status, status information explanation
• Response header field returns information describing
server’s attributes
• Entity body returns HTML page requested by the client
machine
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14. Web Client/Server Architectures (cont’d.)
• Three-tier architecture allows additional processing
before server responds to client’s request
– Often includes databases and related software
applications that supply information to the Web server
• Web server uses software applications’ output when
responding to client requests
• N-tier architectures have more than three tiers
– Track customer purchases stored in shopping carts
– Look up sales tax rates, ;keep track of customer
preferences, update in-stock inventory databases
– Keep product catalog current
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FIGURE 8-3 Message flows in a three-tier client/server network
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16. Operating Systems for Web Servers
• Operating system tasks include running programs,
allocating computer resources to programs, and
proving input and output services
– Required for a computer to run programs
– Larger system responsibilities include tracking
multiple users, ensuring no interference
• Web server operating systems software run on
Microsoft Windows Server products, Linux or UNIX-
based operating systems
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17. Operating Systems for Web Servers
(cont’d.)
• Some companies consider Microsoft operating
system simpler to use than UNIX based systems
– Some concerns about security weaknesses caused
by tight integration of Microsoft products
• Linux is open-source, fast, efficient, easy to install
– Can be downloaded free from the Web but most
companies buy it through a commercial distributor for
the additional utilities and support
• Mandriva, Red Hat, SuSE Linux Enterprise
• Oracle sells Web server hardware with its UNIX-
based operating system Solaris
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18. Web Server Software
• Commonly used programs are Apache HTTP Server
and Microsoft Internet Information Server (IIS)
– Some businesses, such as Google, wrote their own
• Apache dominant Web server software since 1996
– Free and user-supported with other services available
• Microsoft IIS bundled with Microsoft Windows
Server OS and runs only on Windows systems
– Used on many intranets, and small and large sites
that have adopted Microsoft products as standard
– ISS is free but OS it comes with can be expensive
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FIGURE 8-4 Percent of active Web sites that use major Web server
software products

20. Electronic Mail (E-Mail) and
E-Mail Benefits and Drawback
• E-mail used to gather information, execute
transactions and perform electronic commerce tasks
• Reason people originally attracted to the Internet
– Conveys messages in seconds with attachments often
the most important message part
– Most popular form of business communication
• Drawbacks include the time spent answering e-mails
– Burdensome and can take 2 hours per day
• Email attachments can be or contain a computer virus
• Most frustrating and expensive problem is spam
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21. Spam and Solutions to the Spam Problem
• In 2009, the peak year for spam, one 24-hour period
showed 220 billion spam e-mail messages sent
• Spam growth has leveled off and legal and technical
solutions will continue to reduce it
• Benefits reaped by spammers still make it attractive
– Reducing spam approaches require passing laws and
technical changes in Internet mail-handling systems
– Approaches under existing laws and technologies
require cooperation by organizations
– Some tactics can be taken by individual e-mail users
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FIGURE 8-5 Spam as a proportion of all business e-mail

23. Individual User Antispam Tactics
• Using a complex e-mail address reduces the chance
that a spammer can automatically generate it
– Downside is that a complex address can be hard to
remember
• Control e-mail address exposure
– Spammer software robots search for e-mail addresses
on discussion boards, in chat rooms, other online
sources that use email
• Use multiple e-mail addresses
– Switch to another if spammers use one
• Use filtering techniques based on contents
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24. Basic Content Filtering
• Content-filtering techniques differ in terms of content
elements examined, spam indications and how
strictly message classification rules applied
• Basic content filters examine e-mail headers
– Client-level filtering: individual users’ computers
– Server-level filtering: mail server computers
• Black list spam filter looks for known spammers in
incoming messages’ From addresses
• White list spam filter looks for good sender From
addresses in incoming messages
– High false positives rate
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25. Challenge-Response Content Filtering
• Compares all incoming messages to a white list
– If sender is not on the white list, automated e-mail
response sent (challenge)
– Challenge asks sender to reply to e-mail (response)
– Reply must contain response to a challenge
presented in the e-mail
• Designed so human can respond easily
• More information
– Carnegie Mellon University CAPTCHA Project site
• Drawback is potential abuse
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FIGURE 8-6 Example of a challenge that uses distorted letters and numbers
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27. Advanced Content Filtering
• Looks for spam indicators in entire e-mail message
– Indicator identified: message’s spam “score” raised
• Indicator types are words, word pairs, certain HTML
codes, information about where word occurs
– Spammers stop including defined indicators
• Bayesian revision statistical technique uses additional
knowledge to revise earlier probability estimates
– Naïve Bayesian filter software allows users to review
messages and indicate if message is spam (not spam)
– Software gradually learns to identify spam and is correct
about 95% of the time after training
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28. Legal Solutions
• January 2004: U.S. CAN-SPAM law went into effect
– Spam decreased first two months, but returned to
previous levels after no threat of federal prosecution
– Prohibits misleading e-mail message address header
information, deceptive subject headers and transfer of
email addresses
• Some spammers have been prosecuted, fined and
received jail time
– Many use servers outside U.S. (jurisdiction issues)
• Legal solutions have had only limited success
– Expensive to prosecute spammers
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29. Technical Solutions
• Internet design did not include mechanisms ensuring
e-mail sender identity would be know to recipient
• Internet’s communication protocol designed to be a
polite set of rules where a sending computer waits for
acknowledgement that message was received
– Originating computer will slow if acknowledgement is
delayed (must continue to scan for it) and will not send
more messages until acknowledgment received
– Defending (receiving) company must develop way to
identify computers sending spam and delay
acknowledgement
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30. Technical Solutions (cont’d.)
• Computer being spammed can also launch a return
attack called teergrubing (“tar pit”)
– Send e-mail messages back to suspected spamming
computer with the objective of setting a trap that
drags down its ability to send spam
– Concern is that counterattack might violate laws
• Ultimate spam solution could come from new e-mail
protocols providing absolute verification of e-mail
message source
• Currently most effective solutions have been
coordinated efforts to identify and block spammers
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31. Web Site Utility Programs
• TCP/IP supports utility programs (tools)
– Run on Web server or client computers
• E-mail: earliest Internet utility program
– Most important utility
– Key element in electronic commerce strategies
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32. Tracert and Other Route-Tracing Programs
• Tracert (TRACE RouTe) sends data packets to
every computer on path between one computer and
another and clocks packets’ round-trip times
– Provides indication of time message needs to travel
from one computer to another and back
– Ensures remote computer online and pinpoints data
traffic congestion
– Calculates and displays the number of hops between
computers and time to traverse entire one-way path
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FIGURE 8-7 Tracing a path between two computers on the Internet
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34. Telnet and FTP Utilities and
Indexing and Searching Utility Programs
• Telnet program allows a person using one computer
to access files and run programs on a second
computer connected to the Internet
• File Transfer Protocol (FTP) is the part of the
TCP/IP rules that defines formats used to transfer
files between TCP/IP connected computers
• Search engines and indexing programs are
important elements of many Web servers
– When a browser requests a Web site search, engine
compares index terms to the requester’s search terms
to find matching documents
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35. Data Analysis Software
• Web servers capture visitor information and places it
into a Web log file (grows quickly)
• Third-party Web log file analysis programs
summarize information in the file
– Query log file and return gross summary information
or accumulating details
• Popular Web log file analysis programs
– Adobe Analytics, Google Analytics, WebTrends
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36. Link-Checking Utilities
• Dead link displays an error message rather than
Web page when clicked
– Sites with many dead links are said to have link rot
• Link checker utility examines each site page and
reports URLs that no longer exists
– Identifies orphan files which are files on Web server
not linked to a page
– Also includes script checking and HTML validation
– Adobe Dreamweaver includes link-checking program
– Free standing link-checking programs include Elsop
LinkScan and LinxCop
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37. Remote Server Administration
• Web site administrator controls Web site from any
Internet connected computers
– Monitor server activity and manipulate server from
wherever administrator happens to be
• LabTech Software includes remote administration,
link-checking, HTML troubleshooting, site-monitoring
and other utility programs
– Useful in managing the operations on the Web
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38. Web Server Hardware
• Wide variety of computer brands, types, sizes used
by organizations to host online operations
• Small companies run Web sites on desktop PCs
• Most online business operations are operated on
computers designed for site hosting
• Businesses select specific hardware and software
elements based on site’s functionality, expected
visitors, number and size of pages and graphics
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39. Server Computers
• Generally have more memory, larger (faster) hard
disk drives and faster processors than typical
desktop computers
– Many Web server computers use multiple processors
– Most companies spend $2,000-$50,000 on an
individual Web server with large organizations
spending millions on server hardware
• May be housed in freestanding cases but most are
installed in equipment racks
• Blade servers are servers-on-a-card
– Small in size: 300 installed in single 6-foot rack
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FIGURE 8-8 Rack-mounted blade servers

41. Web Servers and Green Computing
• Significant electrical power needs for operating
servers and cooling the room where servers housed
• Green computing is efforts to reduce environmental
impact of large computing installations
• Novel approaches using natural cooling
– Google server facility in Finland
– Facebook server in Lulea, Sweden
– Other companies: Hewlett-Packard, FedEx, Harris
Corporation
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41

42. Web Server Performance Evaluation
• Benchmarking is testing to compare hardware and
software performance and includes many elements
– Hardware, operating system software, server
software, connection speed, user capacity, type of
Web pages delivered and connection bandwidth
– Users server can handle important, hard to measure
• Throughput is the number of HTTP requests
hardware and software process in a unit of time
• Response time is time server requires to process
one request
• Independent testing and benchmarks available
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43. Web Server Hardware Architectures
• Electronic commerce Web sites use tiered architecture
to divide work of serving Web pages
– May use more than one computer within each tier
• Server farms are large collections of servers lined up
row after row
• Centralized architecture uses a few expensive, fast
computers and more sensitive to technical problems
– Requires adequate backup plans
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44. Web Server Hardware Architectures
(cont’d.)
• Distributed architecture (decentralized architecture)
uses many less-powerful, less-expensive computers
– Spreads risk over large number of servers
– Requires additional hubs or switches to connect
servers to each and the Internet
– Requires cost of load balancing to assign the
workload efficiently
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FIGURE 8-9 Centralized and decentralized Web site architectures
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46. Load-Balancing Systems
• Load-balancing switch is network hardware that
monitors server workloads and assigns incoming
Web traffic to the server with most available capacity
– Simple load-balancing system traffic enters through
site’s router and encounters load-balancing switch
which directs traffic to best Web server
– More complex load-balancing systems incoming Web
traffic directed to groups of dedicated Web servers
• Groups organized by specific functions
• Cost of load-balancing systems range from about
$2,000 (simple) to $15,000 - $40,000 (complex)
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FIGURE 8-10 Basic load-balancing system
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FIGURE 8-11 Complex
load balancing system
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49. Cloud Computing
• To reduce costs and effort many businesses are
outsourcing entire networks using cloud computing
– Allows multiple organizations to share a network of
servers and software giving businesses access to
computers, storage and backup at lower cost
– Sometimes called infrastructure as a service (IaaS) or
platform as a service (PaaS)
– Resources can be allocated dynamically as needed
• Some larger firms use hybrid cloud computing
– Move large-volume, routine work to cloud provider and
maintain more sensitive data and processes internally
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FIGURE 8-12 Cloud computing provider global market share, 2015
© Cengage Learning 2015

51. Content Delivery Networks
• Latency occurs when a transmission delay is caused
by network inability to handle full traffic load
– Problem for businesses that rely on Internet to deliver
large audio and video files to customers
• To prevent latency, online businesses have turned to
content delivery networks
– Service that stores large file contents on multiple
servers throughout the Internet for a fee
– Large file requests routed to nearest server with a
stored copy of the file
© 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a
license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 51

52. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a
license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 52
FIGURE 8-13 Growth of Internet traffic, actual and projected